UNLIKELY HERO: Defenseman Radek Martinek celebrates his third period goal against the first-place Canadiens last night in Long Island. Photo: NHLI via Getty Images

Radek Martinek rarely been the offensive star during 11 NHL seasons, so the chance to savor a winning goal was meaningful to the 36-year-old defenseman.

Martinek, injured most of last season, scored the tiebreaker eight minutes into the third period as the Islanders handed the Canadiens their first regulation loss in nearly a month with a 6-3 victory last night.

The quiet Martinek, who had not scored since Oct. 12, 2011, when he was with Columbus, was all smiles as he gave credit to teammates.

“It feels very good to win two straight at home after the struggles we’ve had,” he said, referring to the Islanders winning just twice in their first 11 home games. “Now we have something to build on.”

Martinek’s shot from the left point on a pass from Kyle Okposo eluded goaltender Carey Price at 7:56. John Tavares scored his team-leading 14th goal with 1:07 left before Colin McDonald closed the scoring with an empty-netter.

Brian Gionta’s power-play goal at 6:07 of the third — the 20,000th goal for the Canadiens since the NHL was formed in 1917 — had tied the game at 3.

“This was a tough one for us,” Gionta said. “They are a dangerous offensive team and they have the power when they play their game. We simply didn’t play the way we wanted to play.”

Montreal defenseman P.K. Subban made it 3-2 with a blast from the point with 3:11 to go in the second, his fifth of the season, after Matt Martin and Michael Grabner scored 48 seconds apart midway through the second to put the Islanders ahead 3-1.

The Islanders, who play host to the Rangers tomorrow, won for just the fourth time in 13 games at Nassau Coliseum. They defeated Ottawa in shootout last Sunday after losing to Carolina, Boston and Toronto to begin the homestand.

“I’m always telling the guys that it’s all about consistency from shift to shift,” said winning goaltender Evgeni Nabokov, who stopped 29 shots. “If we play the way we can for 60 minutes, we won’t be easy for any team to beat,”

The 37-year-old goaltender, who improved to 10-7-2, has started all but four games this season.

Montreal hadn’t lost in regulation since a 6-0 defeat at home against Toronto on Feb. 9. The Canadiens surged to the top of the Eastern Conference with an 8-0-3 record since that lopsided defeat.

“This wasn’t our night,” Canadiens coach Michel Therrien said. “The Islanders have good young players. They played a strong game.”

The Canadiens still lead the conference with a 14-5-4 mark. They next play at Carolina on Thursday before heading to play at Tampa Bay and Florida over the weekend.

Martin scored at 12:10 of the second, knocking in a pass from Brad Boyes for his second of the season with Montreal’s Lars Eller serving a tripping penalty. Grabner added his ninth of the season at 12:58 after a shot by defenseman Thomas Hickey deflected to him in front of Price.

Montreal’s Tomas Plekanec opened the scoring at 5:21 of the first with his 10th of the season. Plekanec took a pass from Alex Galchenyuk in the left corner after Michael Ryder outmuscled Martinek in the right corner.

Matt Moulson tied it at 1:23 of the second off a pass from defenseman Mark Streit for his 11th of the season.

The Islanders have won three straight and six of their last eight games against Montreal, including 4-3 in overtime at Montreal on Feb. 21. The teams meet once more this season at Nassau Coliseum on March 21.

It was the fifth contest of a seven-game homestand for the Islanders, who play the Rangers before completing the homestand Saturday against Washington.

“Having the Rangers here will be intense,” Martinek said. “All we can do is continue playing the way we have these past two here at home. It’s really a simple game. You have to play hard every night.”

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The Islanders played without defenseman Lubomir Visnovsky, who had to attend to a family matter. … Left wing Moulson’s games-played streak stands at 269 games. He has yet to miss a game in his Islanders career .